Abstract Non‐heterocytous filamentous cyanobacteria are increasingly recognized as abundant and diverse microbial components of tropical and subtropical mangrove ecosystems. However, taxonomic studies of cyanobacteria in Thailand have largely focused on freshwater and artificial hypersaline environments, leaving mangrove‐associated cyanobacterial communities understudied. In this polyphasic study, cyanobacterial mats were isolated and characterized from mangrove environments along the Andaman coastlines of Ranong and Phang‐Nga provinces. Comparative analysis of morphology, salinity tolerance, habitat preference, 16S rRNA gene phylogeny and genetic similarity, 16S–23S ITS rRNA region phylogeny, secondary structure and percent dissimilarity supported the descriptions of Desertifilum andamanense sp. nov., Tigrinifilum phangngense sp. nov., Roseofilum epilithicum sp. nov., and Persinema corticola sp. nov., while justifying the continued recognition of D. fontinale and D. tharense . Two divergent ITS rRNA region operons in T. floridanum with different leader motifs, D1‐D1', and D2 regions proved to be useful diagnostic markers of the ITS rRNA region for species and strain differentiation within Tigrinifilum . Our results underscore the importance of a polyphasic approach that also considers intragenomic ITS rRNA region variation to ensure robust and accurate taxonomic assessments of cyanobacteria. This study also provides records of the genera Desertifilum , Roseofilum , Tigrinifilum , and Persinema in Thailand, contributing to a more comprehensive understanding of the nation's diversity and biogeography of cyanobacteria.
Ginn et al. (Mon,) studied this question.